Derive Macro for MapEntites (#17611) #18311
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| /// } | ||
| /// | ||
| /// # #[derive(MapEntities)] | ||
| /// # struct TestTuple(A); |
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to eliminate that double newline?
Bleachfuel
suggested changes
Mar 16, 2025
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| match &attr.meta { | ||
| syn::Meta::Path(_) => continue 'fields, | ||
| _ => panic!("just use the bare `#[skip_mapping]`"), | ||
| } |
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just continue without checking! This is unnessesary code
| fn map_struct(name: syn::Ident, fields: &Fields) -> proc_macro2::TokenStream { | ||
| let mut map_entities = vec![]; | ||
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| 'fields: for (i, field) in fields.iter().enumerate() { |
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| 'fields: for (i, field) in fields.iter().enumerate() { | |
| for (i, field) in fields.iter().enumerate() { |
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| match &attr.meta { | ||
| syn::Meta::Path(_) => continue 'fields, | ||
| _ => panic!("just use the bare `#[skip_mapping]`"), | ||
| } |
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Suggested change
| match &attr.meta { | |
| syn::Meta::Path(_) => continue 'fields, | |
| _ => panic!("just use the bare `#[skip_mapping]`"), | |
| } | |
| continue |
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| let map_field = if let Some(field_name) = &field.ident { | ||
| // Named field (struct) | ||
| quote! { | ||
| <#ty as bevy_ecs::entity::MapEntities>::map_entities(&mut self.#field_name, entity_mapper); | ||
| } | ||
| } else { | ||
| // Unnamed field (tuple-like struct) | ||
| let idx = syn::Index::from(i); | ||
| quote! { | ||
| <#ty as bevy_ecs::entity::MapEntities>::map_entities(&mut self.#idx, entity_mapper); | ||
| } | ||
| }; | ||
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| map_entities.push(map_field); |
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Suggested change
| let map_field = if let Some(field_name) = &field.ident { | |
| // Named field (struct) | |
| quote! { | |
| <#ty as bevy_ecs::entity::MapEntities>::map_entities(&mut self.#field_name, entity_mapper); | |
| } | |
| } else { | |
| // Unnamed field (tuple-like struct) | |
| let idx = syn::Index::from(i); | |
| quote! { | |
| <#ty as bevy_ecs::entity::MapEntities>::map_entities(&mut self.#idx, entity_mapper); | |
| } | |
| }; | |
| map_entities.push(map_field); | |
| let member = as_member(&field.ident, i); | |
| map_entities.push(quote! { | |
| <#ty as bevy_ecs::entity::MapEntities>::map_entities(&mut self.#member, entity_mapper); | |
| }); | |
Closed
alice-i-cecile
added
A-ECS
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Objective
instead of writing boilerplate like this
users can now use the derive macro
MapEntities.If any fields dont implement that trait, they can be skipped with a
#[skip_mapping]attribute.Fixes #17611
Solution
My implementation is a heavily simplified version of @Liam19's version, as I didnt want to add too much complexity at once, and I am not familiar with that trait. So feedback is appreciated.
Since its possible that people want to derive enums as well, I have put the derive function in its own file, so that it has space to grow
Testing
Theres now an example in the documentation